The project will concentrate on analysis, at the cellular and molecular levels, of the regulation by juvenile hormone of vitellogenin synthesis in the fat body of the African migratory locust, as a model system for investigating the mode of action of this hormone. The vitellogenin and vitellin proteins have already been characterized, as well as the cytological and biochemical changes that occur in the fat body during induction of synthesis by the juvenile hormone analog, ZR-515, and the general kinetics of the response. In the forthcoming grant period, we intend to clone cDNA prepared from female locust fat body RNA in E. coli and select clones that contain vitellogenin-coding sequences by hybridization with enriched cDNA and mRNA preparations and by their specific effect on vitellogenin translation. This will provide a probe which will be used to measure the synthesis of vitellogenin mRNA in intact animals, in fat body in culture, and in nuclear or chromatin preparations from fat body. Questions to be examined include the kinetics of mRNA synthesis after hormone treatment, with particular attention to lag times and rates during primary and secondary induction; the acquisition of competence of the vitellogenin gene to respond during development of the locust; whether the gene in male fat body can, under any circumstances, be activated. The frequency of this gene in the male and the female genome will be examined. It is hoped also to clone the natural vitellogenin gene or genes isolated from the genome, and to use these clones to examine the organization of coding and possible non-coding sequences. Juvenile hormone binding proteins, as potential hormone receptors, in fat body cytoplasm and nuclei will also be examined. The eventual objectives is to establish the relationship between hormone, receptor, and stimulation of specific transcription in the chromatin.